Control Circuit and Fan Comprising the Same

ABSTRACT

A control circuit and a fan comprising the same are provided. The fan comprises a plurality of windings. The control circuit comprises a temperature sensing module and an adjusting module. The temperature sensing module is configured to sense an environmental temperature to generate a temperature signal. The adjusting module is coupled to the windings and is configured to change a connection between the windings in response to the temperature signal to adjust an impedance value of the fan, wherein the fan is a fan, the adjusting module adjusts the impedance value of the fan in response to the temperature signal to change a rotational speed of the fan.

This application claims the benefit of priority based on China Patent Application No. 200710124058.7 filed on Oct. 22, 2007, the contents of which are incorporated herein by reference in their entirety.

CROSS-REFERENCES TO RELATED APPLICATIONS

Not applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a control circuit and a fan comprising the same. More specifically, the present invention relates to a control circuit capable of adjusting an impedance value in response to an environmental temperature and a fan comprising the same.

2. Descriptions of the Related Art

With the continual development of electronic technologies, more heat is generated by the central processing unit (CPU) and other electronic elements within the computers. Accordingly, stricter requirements have been imposed on the heat dissipation so that the various electronic elements can operate normally under high power and high heat. Generally, one common way to dissipate heat is to provide an additional cooling fan, which is operated by a driving apparatus that rotates at a high speed for quick heat dissipation. On the other hand, to decrease the power consumption of the cooling fan and prolong the service life of the driving apparatus, the driving apparatus is configured to decrease the rotational speed of the cooling fan when the electronic elements operate in a low power mode with much less heat generation.

Conventionally, the driving apparatuses typically employ pulse width modulation (PWM) technology to adjust the rotational speed of the cooling fan. This technology adjusts the rotational speed of the fan by changing the ON and OFF status of the fan in a unit time. Since the typical cooling fans operate at a widely varied rotational speed, the current that the PWM has to adjust also varies widely. Nevertheless, when electronic elements (e.g., a CPU) are generally operated in the lower power mode, the fan has a slower rotational speed to account for the decreased rotational speed. In this case, abrupt variations to the inductor's current induced by the PWM controlling operations will cause considerably loud noise and also increased switching loss.

In summary, it is important to find another means to dynamically adjust the rotational speed of the fan in the driving apparatus in response to the temperature of the electronic elements without incurring additional costs and noise.

SUMMARY OF THE INVENTION

One objective of the present invention is to provide a control circuit applied in a fan comprising a plurality of windings. The control circuit is configured to change a connection between these windings in response to an environmental temperature to adjust an impedance value of the fan to change the rotational speed of the fan. The control circuit comprises a temperature sensing module and an adjusting module. The temperature sensing module is configured to sense the environmental temperature to generate a temperature signal. The adjusting module is coupled to the windings and configured to change the connection between the windings in response to the temperature signal to adjust the impedance value of the fan, wherein a rotational speed of the fan is changed according to the impedance value.

Another objective of the present invention is to provide a fan comprising a plurality of windings and a control circuit. The control circuit comprises a temperature sensing module and an adjusting module. The temperature sensing module is configured to sense an environmental temperature to generate a temperature signal. The adjusting module is coupled to the windings and configured to change a connection between the windings in response to the temperature signal to adjust an impedance value of the fan, wherein a rotational speed of the fan is changed according to the impedance value.

The present invention adjusts the impedance value of the fan by changing the connection between a plurality of windings via the temperature sensing module and adjusting module. Once the impedance value of the fan is changed, the rotational speed of the fan can be adjusted. This will eliminate the loud noise and increased switching loss caused by the abrupt variation to the inductor's current in the conventional PWM controlling method.

The detailed technology and preferred embodiments implemented for the subject invention are described in the following paragraphs accompanying the appended drawings for people skilled in this field to well appreciate the features of the claimed invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating a first embodiment of the present invention;

FIG. 2 is a schematic diagram illustrating a second embodiment of the present invention; and

FIG. 3 is a schematic diagram illustrating a third embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The following embodiments will be described to explain the present invention. The present invention relates to a control circuit and a fan comprising the same. The control circuit is configured to sense an environmental temperature and to change a connection between a plurality of windings in the fan in response to the sensed temperature. The impedance value of the fan is then changed to adjust the rotational speed of the fan. In this way, the present invention effectively prevents the problems of the conventional solutions. However, these embodiments are not intended to limit the present invention to any specific context, applications or particular methods described in these embodiments. Therefore, the description of these embodiments is only intended to illustrate rather than to limit the present invention. It should be noted that in the following embodiments and drawings, the elements not directly related to the present invention are omitted from depiction. Dimensional relationships among individual elements are illustrated only for understanding rather than that to limit the actual scale thereto.

A first embodiment of the present invention is a fan 1 as shown in FIG. 1. The fan 1 comprises a plurality of windings (termed as the first winding 11 and second winding 12 in this embodiment), a control circuit 13, a first switch element 14, and a second switch element 15. In this embodiment, the fan 1 is a fan, while the control circuit 13 is configured to adjust the rotational speed of the fan 1 in response to an environmental temperature. The control circuit 13 comprises a temperature sensing module 131 and an adjusting module 133. The temperature sensing module 131 is configured to sense the environmental temperature to generate a temperature signal 130. The adjusting module 133 is coupled to the first winding 11 and the second winding 12 and also electrically connected to the first switch element 14 and the second switch element 15. As a result, the adjusting module 133 is configured to change a connection between these windings in response to the temperature signal 130 to adjust the overall impedance of the fan 1. More particularly, when the environmental temperature remains within a preset range, the adjusting module 133 sends a first adjusting signal 132 to keep the first switch element 14 turned on and sends a second adjusting signal 134 to keep the second switch element 15 turned off, so that the current will only flow to the winding 12 through the first switch element 14, thus yielding an impedance value to control rotational speed of the fan 1.

When the environment temperature decreases, the first adjusting signal 132 from the adjusting module 133 will turn off the first switch element 14 while the second adjusting signal 134 from the adjusting module 133 will turn on the second switch element 15. The first winding 11 and the second winding 12 are electrically connected in series through the second switching element 15. At this point, the first winding 11 and the second winding 12 will jointly yield an impedance value, which is greater than the impedance value yielded by the first winding 11 solely. For example, assuming that both the first winding 11 and the second winding 12 have an impedance value of 2 ohms (Ω), when the first switch element 14 is turned on and the second switch element 15 is turned off, the fan 1 has an impedance value of 2Ω. In contrast, when the first switch element 14 is turned off and the second switch element 15 is turned on instead, the first winding 11 and the second winding 12 will be electrically connected in series and yield an overall impedance value of 4Ω. As the overall impedance value of the fan 1 is increased, the rotational speed of the fan 1 is decreased. As a result, the power consumption of the fan 1 will decrease.

When the rotational speed of the fan 1 needs to be increased again, the adjusting module 133 changes the first adjusting signal 132 and the second adjusting signal 134 to turn on the first switch element 14 and turn off the second switch element 15. In this way, the rotational speed of the fan 1 can be controlled in response to the on or off status of the first switch element 14 and second switch element 15.

In this embodiment, the first switch element 14 and the second switch element 15 may be Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFET). Connections between the MOSFETs and the first winding 11 and the second winding 12 are well-known to those skilled in the art, and thus a detailed description thereof will be omitted herein.

A second embodiment of the present invention is shown in FIG. 2. The fan 2 comprises a plurality of windings (termed as a first winding 21 and a second winding 22 in this embodiment), a control circuit 23, a first switch element 24, and a second switch element 25. In the second embodiment, the fan 2 is a fan. The control circuit 23 is configured to adjust the rotational speed of the fan 2 in response to the environmental temperature. The control circuit 23 comprises a temperature sensing module 231 and an adjusting module 233. The temperature sensing module 231 is configured to sense the environmental temperature to generate a temperature signal 230. The adjusting module 233 is coupled to the first winding 21 and the second winding 22, and also electrically connected to the first switch element 24 and the second switch element 25. As a result, the adjusting module 233 is configured to change the connection between these windings in response to the temperature signal 230 to adjust the overall impedance of the fan 2. More particularly, when the environmental temperature remains within a preset range, the adjusting module 233 sends a first adjusting signal 232 to keep the first switch element 24 turned on, and sends a second adjusting signal 234 to keep the second switch element 25 turned off, so that current will only flow to the winding 22 through the first switch element 24, thus yielding an impedance value to control the rotational speed of the fan 2.

When the temperature in the environment rises, the second adjusting signal 234 from the adjusting module 233 will turn on the second switch element 25 so that the first winding 21 and the second winding 22 are electrically connected in parallel through the first switch element 24 and the second switching element 25 which are both turned on. At this point, the first winding 21 and the second winding 22 will jointly yield an impedance value, which becomes smaller than the impedance value yielded by the first winding 21 solely. For example, assuming that both the first winding 21 and the second winding 22 have an impedance value of 2Ω, when the first switch element 24 is turned on and the second switch element 25 is turned off, the fan 2 has an impedance value of 2Ω. In contrast, when the first switch element 24 and the second switch element 25 are both turned on in response to the first adjusting signal 232 and the second adjusting signal 234 respectively, the first winding 21 and the second winding 22 will be electrically connected in parallel and yield an overall impedance value of 1Ω. As the overall impedance value of the fan 2 is decreased, the rotational speed of the fan 2 is increased. As a result, the cooling performance of the fan 2 is enhanced.

When the rotational speed of the fan 2 needs to be increased again, the adjusting module 233 changes the first adjusting signal 232 and the second adjusting signal 234 to keep the first switch element 24 turned on and the second switch element 25 turned off. In this way, the rotational speed of the fan 2 can be controlled in response to the on or off status of the first switch element 24 and the second switch element 25.

In this embodiment, the first switch element 24 and the second switch element 25 may be an MOSFET. Connections between the MOSFETs and the first winding 21 and the second winding 22 are well-known to those skilled in the art, and thus a detailed description thereof will be omitted herein.

A third embodiment of the present invention is shown in FIG. 3. The fan 3 comprises a plurality of windings (termed as a first winding 31 and a second winding 32 in this embodiment), a control circuit 33, a first switch element 34, a second switch element 35, and a third switch element 36. In the third embodiment, the fan 3 is a fan. The control circuit 33 is configured to adjust the rotational speed of the fan 3 in response to the environmental temperature. The control circuit 33 comprises a temperature sensing module 331 and an adjusting module 333. The temperature sensing module 331 is configured to sense the environmental temperature to generate a temperature signal 330. The adjusting module 333 is coupled to the first winding 31 and the second winding 32, and also electrically connected to the first switch element 34, the second switch element 35 and the third switch element 36. As a result, the adjusting module 333 is configured to change the connection between these windings in response to the temperature signal 330 to adjust an overall impedance value of the fan 3. More particularly, when the environmental temperature remains within a preset range, the adjusting module 333 sends a first adjusting signal 332 to turn off the first switch element 34, sends a second adjusting signal 334 to turn on the second switch element 35, and sends a third adjusting signal 336 to turn off the third switch element 36, so that current will only flow to the winding 32 through the second switch element 35, thus yielding an impedance value to control the rotational speed of the fan 3.

When the environment temperature decreases, the first adjusting signal 332 from the adjusting module 333 will turn on the first switch element 34. The second adjusting signal 334 and the third adjusting signal 336 from the adjusting module 333 will turn off the second switch element 35 and the third switch element 36 respectively, so that the first winding 31 and the second winding 32 are electrically connected in series through the first switching element 34. At this point, the first winding 31 and the second winding 32 will jointly yield an impedance value, which is greater than the impedance value yielded by the first winding 31 solely. For example, assuming that both the first winding 31 and the second winding 32 have an impedance value of 2Ω, when the second switch element 35 is turned on, and the first switch element 34 and the third switch element 36 are turned off, the fan 3 has an impedance value of 2Ω. In contrast, when the first switch element 34 is turned on, and the second switch element 35 and the third switch element 36 are turned off, the first winding 31 and the second winding 32 will be electrically connected in series and yield an overall impedance value of 4Ω. Since the overall impedance value of the fan 3 is increased, the rotational speed of the fan 3 is decreased As a result, power consumption of the fan 3 will decrease.

On the other hand, when the environment temperature increases, the second adjusting signal 334 and the third adjusting signal 336 from the adjusting module 333 will turn on the second switch element 35 and the third switch element 36 respectively. The first adjusting signal 332 from the adjusting module 333 will turn off the first switch element 34 so that the first winding 31 and the second winding 32 are electrically connected in parallel through the second switch element 35 and the third switching element 36 which are both turned on. At this point, the first winding 31 and the second winding 32 will jointly yield an impedance value, which is smaller than the impedance value yielded by the first winding 31 solely. For example, assuming that both the first winding 31 and the second winding 32 have an impedance value of 2Ω, when the second switch element 35 is turned on while the first switch element 34 and the third switch element 36 are turned off, the fan 3 has an impedance value of 2Ω. In contrast, when the second switch element 35 and the third switch element 36 are turned on in response to the second adjusting signal 334 and the third adjusting signal 336 respectively, the first winding 31 and the second winding 32 will be electrically connected in parallel and yield an overall impedance value of 1Ω. As the overall impedance value of the fan 3 is decreased, the rotational speed of the fan 3 is increased. As a result, the cooling performance of the fan 3 is enhanced.

In other words, in the third embodiment, the connection between the windings may be either a series connection, parallel connection, or a combination thereof. Through various combinations of the winding connections, a plurality of rotational speed ranges can be defined by different winding connection.

In this embodiment, the first switch element 34, the second switch element 35 and the third switch element 36 may be a MOSFET. Connections between the MOSFETs and the first winding 31 and the second winding 32 are well-known to those skilled in the art, and thus a detailed description thereof will be omitted herein.

Furthermore, in each of the rotational speed ranges defined by the changing overall impedance value of the windings, the fine tuning of the rotational speed can be further accomplished by the adjusting module 333 through pulse width modulation (PWM), which is well-known to those skilled in the art and thus will not be described in detail again.

In summary, the present invention can use a temperature sensing module and an adjusting module to adjust the overall impedance value of a fan by changing the connection between the windings. The change of the impedance value will lead to an adjustment of the rotational speed of the fan to obviate the loud noise and increased switching loss caused by the abrupt variation to the inductor's current in the conventional PWM controlling method. Meanwhile, the adjustability of the rotational speed will lead to further decreased power consumption of the fan.

The above disclosure is related to the detailed technical contents and inventive features thereof. People skilled in this field may proceed with a variety of modifications and replacements based on the disclosures and suggestions of the invention as described without departing from the characteristics thereof. Nevertheless, although such modifications and replacements are not fully disclosed in the above descriptions, they have substantially been covered in the following claims as appended. 

1. A control circuit applied in a fan, the fan comprising a plurality of windings, the control circuit comprising: a temperature sensing module configured to sense an environment temperature to generate a temperature signal; and an adjusting module, being coupled to the windings and configured to change connection between the windings in response to the temperature signal to adjust an impedance value of the fan; wherein a rotational speed of the fan is changed according to the impedance value.
 2. The control circuit as claimed in claim 1, wherein the connection between the windings is one of series connection, parallel connection, and a combination thereof.
 3. The control circuit as claimed in claim 1, wherein the windings comprises a first winding and a second winding, the fan further comprises a switch element, the adjusting module outputs an adjustment signal in response to the temperature signal to turn on the switch element, and the first winding and the second winding are coupled in series via the switch element to adjust the impedance value of the fan.
 4. The control circuit as claimed in claim 1, wherein the windings comprises a first winding and a second winding, the fan further comprises a first switch element and a second switch element, the adjusting module outputs an adjustment signal in response to the temperature signal to turn on the first switch element and the second switch element, and the first winding and the second winding are coupled in parallel via the first switch element and the second switch element to adjust the impedance value of the fan.
 5. The control circuit as claimed in claim 4, wherein one of the switch elements is a metal-oxide-semiconductor field-effect transistor (MOSFET).
 6. The control circuit as claimed in claim 1, wherein the adjusting module changes the rotational speed of the fan through the pulse width modulation (PWM).
 7. A fan, comprising: a plurality of windings; and a control circuit, comprising: a temperature sensing module configured to sense an environment temperature to generate a temperature signal; and a adjusting module, being coupled to the windings and configured to change connection between the windings in response to the temperature signal to adjust an impedance value of the fan; wherein a rotational speed of the fan is changed according to the impedance value.
 8. The fan as claimed in claim 7, wherein the connection between the windings is one of series connection, parallel connection, and the combination thereof.
 9. The fan as claimed in claim 7, wherein the windings comprises a first winding and a second winding, the fan further comprises a switch element, the adjusting module outputs an adjustment signal in response to the temperature signal to turn on the switch element, and the first winding and the second winding are coupled in series via the switch element to adjust the impedance value of the fan.
 10. The fan as claimed in claim 7, wherein the windings comprises a first winding and a second winding, the fan further comprises a first switch element and a second switch element, the adjusting module outputs an adjustment signal in response to the temperature signal to turn on the first switch element and the second switch element, and the first winding and the second winding are coupled in parallel via the first switch element and the second switch element to adjust the impedance value of the fan.
 11. The fan as claimed in claim 10, wherein one of the switch elements is a metal-oxide-semiconductor field-effect transistor.
 12. The fan as claimed in claim 7, wherein the adjusting module changes the rotational speed of the fan through the pulse width modulation. 